1. Field of the Invention
The present invention relates to a protocol for enabling radios or nodes to acquire access for transmissions in a mobile communications network.
2. Discussion of the Known Art
The recent shift toward isolated urban military warfare emphasizes the need for rapidly deployable, multihop tactical networks. Due to inherent characteristics of wireless signals, simultaneous transmissions of voice or other communications are usually difficult to implement over multiple hops without costly hardware and/or a network controller, however. And because typical military handheld radios are usually in the form of single channel, half-duplex transceivers due to size, weight and power (SWAP) considerations, the radios have limited if any capability to coordinate simultaneous communications within a given network. While a central base station like one defined in IEEE Standard §802.16 or used in commercial cellular networks could provide such coordination, the base station would become vulnerable as a single point of failure.
Existing mobile ad hoc networks (MANET) may also rely on known static time domain multiple access (TDMA) schemes such as Link 16 to carry out simultaneous communications. Static TDMA networks are typically pre-planned and are not adaptive, and require certain critical network nodes that add to network vulnerability, however.
MANETs can also deploy a carrier sense multiple access/collision avoidance (CSMA/CA) protocol including a request-to-send/clear-to-send (RTS/CTS) mode, to avoid so-called hidden node situations wherein two radios outside of hearing range (i.e., hidden) from one another attempt to transmit data packets at the same time. See, e.g., IEEE Standard §802.11. Without RTS/CTS, a receiver within range of two hidden transmitting nodes would receive sets of collided packets and thus be unable to decode packets as originally transmitted from either radio. RTS/CTS generates additional overhead and unnecessarily limits channel traffic only to unicast messages, however. Yet, unless some form of scheduling or coordination is used in a MANET, packet collisions are inevitable.